Varicose veins are an example of a disease which can occur in a lumen of a living body. Veins in a living body have venous valves for returning blood to the heart against the effects of gravity. When a venous valve fails, a blood backflow occurs to raise the venous pressure and to expand the vein, resulting in onset of varicose veins.
There are various methods for treatment of varicose veins. Examples of such treatment methods include: (1) compression therapy in which the varicose vein is compressed with elastic bondage or the like to improve stagnation of blood, (2) sclerotherapy in which a sclerosing agent is injected into the vein to induce a trauma in the blood vessel wall, thereby clogging up the blood vessel lumen, (3) vein stripping, i.e., stripping in which the vein is extracted, (4) laser therapy in which the vein is thermally occluded by laser irradiation, and (5) radiofrequency (RF) therapy in which the vein is occluded by heat generated by passing an RF current from an electrode.
U.S. Pat. No. 7,396,355 discloses a treating method in which after injection of a tumescent local anesthesia (TLA) fluid from a syringe into the tissue surrounding a blood vessel to be treated, a catheter provided with electrodes at its distal end is inserted into the blood vessel, and an RF current is passed via the electrodes put in contact with the blood vessel wall to ablate the blood vessel tissue, thereby occluding the blood vessel. In this case, the TLA is used to restrain the pain, to prevent burn of the skin, and to reduce the blood vessel diameter.